This invention relates generally to portable telephone apparatus and more particularly to portable radiotelephones which utilize switches or similar elements for control functions and a keypad for dialing telephone numbers.
Telephones having a rotary or pushbutton dial mechanism and other buttons integral to the handset portion have become commonplace in landline subscriber stations. This arrangement offers the telephone user the convenience of bringing the user interface mechanism and control buttons close to the user.
Radiotelephone operation, such as that offered in cellular radiotelephone or in cordless telephone sets, provide a mobility to the telephone user which landline telephone does not provide. The lack of a cord and the small size of the portable radiotelephone unit enables the user to carry the unit essentially wherever the user goes. This portability, however, allows the portable unit to be placed in locations where foreign objects may come in contact with the user interface mechanism and activate number or control buttons. Some protection may be offered by a device which covers the user interface mechanism and control buttons when not in use but small objects such as coins, paperclips, etc. may be trapped between the cover and the mechanism. Undesired operation of buttons in a radiotelephone setting may turn the equipment on or off, cause transmission of unwanted signals and prevent use of a radio channel, or cause undesired functions to occur. Such undesired activation of buttons is likely to engage functions which reduce the operating life of the battery which powers the portable unit.
Some cordless telephones have been offered in the United States which disable the dialling, number memory, and call processing functions when a cover is closed over the dialling keypad. One such cordless telephone is manufactured by the Panasonic Company as model number KXT3000. While offering protection against false telephone number and call processing, the on-off switch and volume control remain subject to undesired activation. Although it might appear that simply turning the unit on or off when the cover is closed would solve all unwanted operation, an operational state is necessary in which the unit is capable of receiving a call and alerting the user but not of taking any other unwanted actions. Such a call receiving state should be enabled by the user and not be subject to accidental deactivation by an unwanted switching off of the unit. Furthermore, if the unit has purposefully been switched off by the user, it should not be unusually subject to being accidentally switched on.